Solar Impulse unveil new round-the-world solar aircraft

Jeremy Wilks

A new solar-aircraft which is capable of flying around the world fuelled only by the Sun has been unveiled in Switzerland.

Solar Impulse 2 has huge wings the width of a Boeing 747, covered in solar cells as thin as a human hair. At its centre is a cockpit that will house one of the two Swiss pioneers who will pilot the machine – Bertrand Piccard and André Borschberg.

The aircraft is an evolution of the Solar Impulse prototype which broke a succession of world records for solar-powered flight last year, including a memorable tour of Europe and a multi-stage trip across America from coast to coast. It also crucially flew all day and all night, powered by the batteries on board which had been charged by the solar cells during the day.

An aircraft designed to travel

Borschberg spoke to Euronews about the project, and began by describing the new aircraft as ‘a major step up compared to the first one’.

“The first airplane was a kind of flying laboratory, and the second airplane we’re launching now is an airplane designed to travel,” Borschberg says.

One of the biggest challenges in the round-the-world flight is the length of each step of the journey. It’s 35,000 kilometres around the world, and at the gentle cruise achieved by a solar powered plane – anywhere between 36 km/h and 140km/h, depending on altitude and wind – the pilots may spend five days aloft, alone inside the cockpit.

“And for that it has to be reliable,” says Borschberg. “We will cross oceans, we will have to fly at least 120 hours, which is ten times more than regular commercial flights, so reliability becomes that much more important.”

Robust technology

Solar Impulse 2 will have to set off from the coast of China with only a vague idea what the weather will be like the other side of the ocean in five or six days time.

So the new aircraft is a lot more robust than its predecessor: “We needed a plane with a lot more energy reserves, capable to fly through clouds, which the first one can’t do,” Borschberg explained.

Much of the technology on board in terms of solar cells and carbon fibre structure is an evolution of the first Solar Impulse, rather than a revolution, but the pilot is particularly proud of the electric motors: “We have electric motors now which have up to 94% efficiency, including the electronics, the gearbox and the motor itself, which is amazingly high.”

The route

The current plan is to set off from somewhere in the Middle East at the beginning of March 2015. “Operationally it makes sense to start there because we’d like to fly over India and China before the monsoon starts.”

“The goal is to start crossing the Pacific starting from April 15th. So the entire flight flying times may take about 20 days and nights, but spread over three months.”

The first few legs across India and China are expected to be relatively short, as the pilots get used to flying the plane and work out any technical niggles that may occur. Then the first big stretch of flight will be across the Pacific Ocean.

Short naps and hypnosis

The aircraft itself is capable of almost endless flight, but that isn’t the case for the pilot, alone in the cockpit, who will have to stay awake and alert for extended periods of several days.

Piccard and Borschberg have simulated the experience in the laboratory. Inside the cockpit they have a small sleeping area, and are expected to take 20-minute cat naps throughout the flight – a practice known as polyphasic sleep.

“I did this at altitude, I did this in the decompression chamber, I did this in the flight simulator,” Borschberg explains. “So it’s a question of understanding yourself, seeing when you get tired, how you react, how you cope with it, how you can relax and recover if you have these short naps.”

“I do a lot of yoga and meditation and breathing techniques which I have used, and Bertrand is using self-hypnosis to relax and get his energy back.”
“It’s not a question of being physically fit, it’s more to be mentally extremely well prepared,” he stresses.

Piloting a solar-powered plane

The new aircraft hasn’t flown yet, but Borschberg expects it to be similar to its predecessor, with slow reactions that demand patience and anticipation from the pilot.

He is particularly fond of the new cockpit design: “First of all it’s beautiful, it’s imposing in some ways, and in the future it’s going to be a place where we will live many days and many nights, and when you fly for a long time in this kind of environment it becomes like a home, you get an emotional relationship with this environment. And so after five days and five nights in some ways it will be difficult to get out!”

And what if something goes wrong mid-Atlantic? The pilots have an integrated parachute and life raft in their seats, and they plan to be prepared: “We do a lot of survival training, in June we will train with the German navy in the North Sea, we will train with the Swiss Army also.”